1. Field of the Invention
The present invention relates to an image forming apparatus such as an electrophotographic image forming apparatus to which a contact electrifying means is applied, and a process cartridge which is detachably attachable onto the image forming apparatus.
In this specification, the electrophotographic image forming apparatus is so adapted as to form an image on a recording medium by using an electrophotographic image forming system. The electrophotographic image forming apparatus is exemplified by an electrophotographic copying machine, an electrophotographic printer (for example, a laser beam printer and an LED printer), a facsimile machine, a word processor and so on.
Also, the process cartridge is so adapted as to integrate an electrifying means with a developing means and an electrophotographic photosensitive member drum into a cartridge, and to make the cartridge detachably attachable to an electrophotographic image forming apparatus main body. Also, the process cartridge is so adapted as to integrate the electrifying means with the electrophotographic photosensitive member drum into a cartridge so as to be detachably attachable on the electrophotographic image forming apparatus main body.
2. Related Background Art
Up to now, in an image forming apparatus using an electrophotographic image forming process, there is applied a process cartridge system in which the electrophotographic photosensitive member and the process means that affects the electrophotographic photosensitive member are integrated into a cartridge, and the cartridge is detachably attached to the image forming apparatus.
The process cartridge system can remarkably improve the operability since the maintenance of the device can be conducted by a user per se without relying on a service man. For that reason, the process cartridge system has been widely employed in the image forming apparatus.
In the above-mentioned image forming apparatus and process cartridge, an electrifying process for electrifying an image bearing member to a uniform potential is required in formation of an electrostatic latent image on the image bearing member, and a corona electrifying apparatus (non-contact with the image bearing member) has been frequently employed as the electrifying apparatus. However, the corona electrifying apparatus has suffered from such problems in that a large amount of ozone is generated, and that a high voltage of about 10 kV must be applied between the electrifying apparatus and the image bearing member, and so on.
As the electrifying means that solves the above problems, in recent years, a so-called contact electrifying apparatus, in which a voltage is applied to an electrifying member that is in direct contact with the image bearing member to uniformly electrify the image bearing member, has been proposed and put in practical use.
A representative one of the above-mentioned contact electrifying apparatus is a roller electrifying apparatus in which a middle-resistant layer is disposed on a front layer of a conductive base roller, and the roller is rotated in accordance with the rotation of the image bearing member. A predetermined voltage is applied between the roller and the image bearing member by a power supply, to thereby electrify the image bearing member to a uniform potential.
There are two voltage applying methods stated below:
1) a method of applying only a d.c. voltage; and
2) a method of applying a voltage resulting from superimposing an a.c. voltage on a d.c. voltage.
In case of the above method 1), for example, in order to set the potential of the image bearing member to xe2x88x92600 V, it is necessary to apply a voltage of about xe2x88x921300 V to the electrifying member. In case of the above method 2), the potential of the image bearing member can be similarly set to xe2x88x92600 V by applying a d.c. voltage of xe2x88x92600 V and a superimposed a.c. voltage of 1500 Vpp or higher.
In this case, the electrifying mechanism complies with the Paschen""s law in any case, in which a discharge phenomenon occurs in a region that satisfies Paschen""s law to electrify the image bearing member when the roller and the image bearing member are located at a specific distance.
However, the contact electrifying apparatus of this type conducts the same operation as that of the corona discharging device that has been initially described, and generates ozone, although the amount of ozone is remarkably suppressed as compared with the corona electrifying apparatus, as is apparent from the above-mentioned electrifying mechanism. Ozone generates nitrogen oxide and leads to a phenomenon that, in the case where nitrogen oxide sticks onto the image bearing member, an image defect occurs due to electrifying failure because the resistance of nitrogen oxide is low.
Under the circumstances, Japanese Patent Application Laid-open No. 6-3921 has proposed an electrifying process that eliminates the above-mentioned problem of ozone occurrence and can further lower a voltage applied to the electrifying apparatus with the elimination of the above-mentioned problem.
In this electrifying process the surface potential of the image bearing member can be set to substantially the same potential as the voltage applied to the electrifying apparatus. This is enabled by performing charge injection to the image bearing member by directly transferring the charges with respect to the image bearing member surface that is in contact with the electrifying member without using the discharge phenomenon.
As the electrifying apparatus for realizing the above-mentioned injection electrifying process, a sponge roller electrifying apparatus will be described. In this type, relatively low resistant particles (conductive particles), which are called charge accelerating particles, are stuck on a blank shell portion in the surface of the electrifying sponge roller that is in contact with the image bearing member. The contact electrifying system (direct injection electrifying) using the charge accelerating particles has been disclosed in Japanese Patent Application Laid-open No. 10-307454, Japanese Patent Application Laid-open No. 10-307455, Japanese Patent Application Laid-open No. 10-307456, Japanese Patent Application Laid-open No. 10-307457, Japanese Patent Application Laid-open No. 10-307458, Japanese Patent Application Laid-open No. 10-307459, and so on. In this system, a d.c. voltage of xe2x88x92600 V is applied to the electrifying sponge roller by a power supply. For that reason, a portion of the image bearing member which is in contact with the electrifying sponge roller is going to have the same potential as the d.c. voltage. In this situation, if charges are injected from the electrifying sponge roller to the image bearing member over the energy barrier of the image bearing member surface, the image bearing member is electrified. On the other hand, in the case where the charges are again moved to the electrifying sponge roller from the image bearing member when the charges cannot go over the energy barrier or the electrifying sponge roller and the image bearing member are spaced apart from each other, the image bearing member is not electrified. This phenomenon largely depends on the energy barrier or the charge retaining capacity of the surface of the image bearing member, whereas if the phenomenon is considered as a competing reaction, the frequency of opportunities that the electrifying sponge roller comes in contact with the image bearing member becomes important.
In order to increase the frequency, it is effective to stick the charge accelerating particles onto the surface of the electrifying sponge roller to enhance the adhesion of the electrifying sponge roller with the image bearing member, and to reverse the rotating direction of the electrifying sponge roller with respect to the forward direction of the image bearing member (the contact surfaces of the image bearing member and the electrifying sponge roller move in opposite directions while being abrasively slid on each other) to increase the relative speed, to thereby increase the number of times the image bearing member contacts the electrifying sponge roller per unit time.
With the above-mentioned structure, the surface potential of the image bearing member is set to substantially the same potential of xe2x88x92600 V which is applied to the electrifying sponge roller, and uniform electrifying is enabled in a micro portion without any electrifying unevenness.
The charge accelerating particles remain on the image bearing member without being transferred onto a transfer paper by a transferring apparatus by making the electrifying polarity of the charge accelerating particles opposite to that of a developer, and the charge accelerating particles are collected on the electrifying sponge roller, to thereby always obtain a new injection site.
In this type, after an image on the image bearing member has been transferred, a non-transferred developer can have appropriate charges by conducting charge injection as in the image bearing member while the non-transferred developer passes between the charge accelerating particles that is being subjected to the electrifying process and the image bearing member. Therefore, the non-transferred developer is collected in a developing apparatus without passing through a region where the developing process is conducted as it is. Therefore, it is possible to realize an electrophotographic process having no cleaner.
However, there is a case in which there occurs the deterioration of electrifying performance due to a long-period use, and in more detail, the deterioration of the electrifying uniformity in the above-mentioned injection electrifying system. This is caused by a reduction of a contact area of the charge accelerating particles and the image bearing member mainly due to the developer as an insulator stored on the electrifying sponge roller bits by bits.
The present invention has been made in view of the above-mentioned circumstances, and therefore an object of the present invention is to provide an image forming apparatus and a process cartridge both using a contact electrifying means, which properly maintain the electrifying performance over a long-period use.
An image forming apparatus according to the present invention to which a process cartridge having an image bearing member, a contact electrifying member for the image bearing member, detection means for detecting a developer remaining amount and storage means is detachably attachable, is characterized by comprising: first drive means for rotationally driving the image bearing member; second drive means for rotationally driving the contact electrifying member; and control means for controlling driving speeds of the first drive means and the second drive means, in which the control means controls the driving speed of the second drive means on the basis of a rotation speed of the second drive means stored in the storage means.
Another image forming apparatus according to the present invention to which a process cartridge having an image bearing member, a contact electrifying member for the image bearing member, detection means for detecting a developer remaining amount and storage means is detachably attachable, is characterized by comprising: first drive means for rotationally driving the image bearing member; second drive means for rotationally driving the contact electrifying member; and control means for controlling driving speeds of the first drive means and the second drive means and calculating the accumulated abrasive sliding distance of the image bearing member and the contact electrifying member: in which the storage means stores one or more rotation speeds of the second drive means corresponding to the accumulated abrasive sliding distance; and the control means controls the driving speed of the second drive means on a basis of the rotation speed stored in the storage means.
Another image forming apparatus according to the present invention to which a process cartridge having an image bearing member, a contact electrifying member for the image bearing member, detection means for detecting a developer remaining amount and storage means is detachably attachable, is characterized by comprising: first drive means for rotationally driving the image bearing member; second drive means for rotationally driving the contact electrifying member; and control means for controlling driving speeds of the first drive means and the second drive means, calculating the accumulated abrasive sliding distance of the image bearing member and the contact electrifying member, and writing two or more of the calculated values and the developer remaining amount or developer consumption amount detected by the detecting means in the storage means, respectively, in which the control means calculates a rotation speed of the second drive means on the basis of two or more of the accumulated abrasive sliding distances and the developer remaining amount or developer consumption amount stored in the storage means to control the second drive means on the basis of the calculated value.
Another image forming apparatus according to the present invention to which a process cartridge having an image bearing member, a contact electrifying member for the image bearing member, detection means for detecting a developer remaining amount and storage means is detachably attachable, is characterized by comprising: first drive means for rotationally driving the image bearing member; second drive means for rotationally driving the contact electrifying member; and control means for rotationally controlling the first drive means at a plurality of drive speeds, and for controlling the driving speed of the second drive means so that the drive speed of the first drive means and the drive speed of the second drive means becomes identical.
Another image forming apparatus according to the present invention is characterized by comprising: an image bearing member, a contact electrifying member for the image bearing member, storage means for storing data according to a developer remaining amount, and control means for variably controlling peripheral speeds of the image bearing member and the contact electrifying means in accordance with the data stored in the storage means. Another image forming apparatus according to the present invention is characterized by comprising: an image bearing member, a contact electrifying member for the image bearing member, storage means for storing data according to a used developer amount, and control means for calculating an accumulated abrasive sliding distance of the image bearing member and the contact electrifying member to variably control peripheral speeds of the image bearing member and the contact electrifying means in accordance with the calculated value and the data stored in the storage means.
A process cartridge according to the present invention which is detachably attachable to an image forming apparatus including first drive means for rotationally driving an image bearing member, second drive means for rotationally driving a contact electrifying member, and control means for controlling driving speeds of the first drive means and the second drive means, is characterized by comprising: the image bearing member, the contact electrifying member for the image bearing member, detection means for detecting a developer remaining amount, and storage means for storing a rotation speed for changing the drive speed of the second drive means.
Another process cartridge according to the present invention which is detachably attachable to an image forming apparatus including first drive means for rotationally driving an image bearing member, second drive means for rotationally driving a contact electrifying member, and control means for controlling driving speeds of the first drive means and the second drive means and calculating the accumulated abrasive sliding distance of the image bearing member and the contact electrifying member, is characterized by comprising: an image bearing member; a contact electrifying member for the image bearing member; detection means for detecting a developer remaining amount; and storage means for storing at least one rotation speed corresponding to the accumulated abrasive sliding distance for controlling the driving speed of the second drive means.
Another process cartridge according to the present invention which is detachably attachable to an image forming apparatus including first drive means for rotationally driving an image bearing member, second drive means for rotationally driving an contact electrifying member, and control means for controlling the driving speeds of the first drive means and the second drive means and calculating the accumulated abrasive sliding distance of the image bearing member and the contact electrifying member, is characterized by comprising: an image bearing member; a contact electrifying member for the image bearing member; detection means for detecting a developer remaining amount; and storage means for storing two or more of the accumulated abrasive sliding distance, and the developer remaining amount or developer consumption amount therein.
According to the present invention, the rotation speed of the contact electrifying member is raised up to a speed written in the storage means in accordance with the developer consumption amount detected by the detection means for detecting the amount of developer, to thereby increase the opportunities of contact of the contact electrifying member with the image bearing member, whereby the electrifying property can be maintained over a long period of time.
Also, the rotation speed is increased by conducting the optimum control of the contact electrifying member by using the developer consumption amount and the abrasive sliding distance between the image bearing member and the contact electrifying member, thereby being capable of maintaining the electrifying property over a long-period use by effectively utilizing the image bearing member lifetime margin.
Also, the rotation speed control of the contact electrifying member is conducted at multiple stages, thereby conducting accurate control regardless of the printing ratio and the variation of the amount of sheets that are continuously printed and maintaining the process cartridge electrifying property for a long period of time.
Since the abrasive sliding target value is made to gradually approach an abrasive sliding limit value, the rotation speed of the contact electrifying member can be gradually increased, thereby maintaining the process cartridge electrifying property for a long period of time.
Since the lifetime of the image bearing member is managed not by an abrasive sliding period of time but an abrasive sliding distance, even if a plurality of image forming process speeds are provided, the lifetime of the image bearing member can be accurately managed.
Also, since the histories of the developer consumption amount and the abrasive sliding distance are recorded in the storage means of the process cartridge, even if the process cartridge is used in another image forming apparatus main body, the electrifying property can be maintained by the optimum contact electrifying member control for a long period of time.
Also, since the histories of the developer consumption amount and the abrasive sliding distance are recorded in the storage means of the process cartridge, after the use of the process cartridge is ended, the process cartridge is collected and the histories of the developer consumption amount and the abrasive sliding distance, which are recorded in the storage means, are read, and the read data is analyzed, thereby determining the use state by a user in more detail.
Also, even if a specification is changed in the process cartridge, if data that is stored in the storage means is changed, the optimum rotation speed of the contact electrifying member can be maintained without adding a change to the image forming apparatus main body.
Also, since the rotation control algorithm of the contact electrifying member is stored in the process cartridge, an improvement of the algorithm can be readily sequentially provided to the user, thereby providing the capability of customizing the algorithm with respect to a specific user.
In the case where an image bearing member abrasion amount (drum abrasion amount) has a margin under the user state by the user, the contact electrifying member rotation speed is changed in accordance with the margin, thereby providing the capability of widening the latitude of the electrifying uniformity.